The Toyota FCV Concept was unveiled this past week. Will it have the same impact as Toyota's Prius? Photo credit: Toyota

Hybrids were just a technological curiosity when Toyota (TM 0.92%) rolled out its first Prius way back in 1997. 

The idea of hybrids had been around for years, but Toyota was the first to mass-produce one. Now, hybrids are a mainstream choice — and a big business. 

That first Prius has become a whole family of vehicles, and Toyota has sold over 3 million of them. 

But Toyota might be moving to disrupt its own success. This past week, Toyota unveiled a new "green" car, this one powered by hydrogen. Will it put the Prius out to pasture?

Why fuel cells could be better than batteries

Officially, the Toyota FCV Concept is just a show car. But Toyota says that it, or something like it, will come to market "around 2015."

The FCV Concept is an electric car, but it doesn't have a battery pack. Instead, it's powered by a fuel cell, a device that converts the chemical energy in hydrogen to electricity. 

Hydrogen fuel cells are very environmentally friendly. A fuel cell car's only "exhaust" is water vapor. But a fuel cell car can't be recharged like regular electric cars. Instead, it needs to be filled up with gas — hydrogen gas.

That's a challenge, but not a big one. Hydrogen is the most abundant element in the universe. Hydrogen gas can be made from natural gas, or even from water.

Many scientists think that fuel cells could be a better choice than battery packs for the electric cars of the future. Even the best electric-car batteries of today are still very heavy, and very expensive. 

That means designers of battery-electric cars have two choices: Limit the car's range to 100 miles or so to keep the car's size and price down, as Nissan (NSANY -1.09%) did with its Leaf. Or build a heavy car with a big price tag that gets good range, as Tesla Motors (TSLA 11.96%) has done with its Model S. 

Fuel cells allow electric-car designers to have their cake and eat it, too. 

The Toyota FCV isn't the only fuel-cell car headed to market
The Toyota FCV Concept is just one of several fuel-cell cars coming to market in the next few years. Hyundai (HYMTF 4.75%) has said that it will bring a fuel-cell-powered SUV to the U.S. market in 2015. That's not a token gesture — Hyundai hopes to sell 10,000 a year.

Hyundai's ix35 Fuel Cell is based on the Tucson SUV. It has already been produced in small numbers. Hyundai hopes to be selling 10,000 a year in a few years. Photo credit: Hyundai

Meanwhile, Ford (F -0.04%) is working with Nissan and Daimler (MBGA.F -0.42%), the corporate parent of Mercedes-Benz, on a project that will bring fuel cell cars to market by 2017, they say. The three are sharing development costs in hopes of designing better technology more quickly.

Likewise, General Motors (GM -0.34%) and Honda (HMC -0.51%) are teaming up on a fuel-cell design of their own. Most other big automakers are doing similar work, or are expected to follow suit.

But will these fuel cell cars really replace hybrids and battery-electrics — not to mention the gasoline-powered cars that most of us drive, that still seem to get better every year?

Are fuel cell cars really the future?
It's hard to say, and these companies are all hedging their bets. Even as they work on fuel cell cars, Toyota and Ford (and most of the others) are investing big in better hybrids, and continuing work on battery-electric cars, and developing ever-more-efficient gasoline engines, too.

Tesla Motors has gone all-in on batteries, and Tesla CEO Elon Musk has made it clear that he thinks fuel cells are not a serious solution. But big automakers like Toyota and its peers aren't convinced, as their big investments in fuel cell cars like the FCV show.

They seem determined to try all the technologies that make sense — and leave it up to consumers to decide what works best.